The disclosure of Japanese Patent Application Nos. HEI 11-334526 filed on Nov. 25, 1999, 2000-89771 filed on Mar. 28, 2000 and 2000-316425 filed on Oct. 17, 2000, including the specifications, drawings, and abstracts are incorporated herein by reference in their entirety.
1. Field of the Invention
The invention relates to an internal combustion engine equipped with a variable valve train capable of arbitrarily altering the opening and closing timing and/or the opening amount of at least one of an intake valve and exhaust valve. In particular, the invention relates to a technology for favorably generating intake pipe negative pressure in an intake passage in an internal combustion engine.
2. Description of the Related Art
Recent years have seen the development of internal combustion engines equipped with a variable valve train capable of altering the opening and closing timing and/or the opening amount of at least one of an intake valve and exhaust valve in an internal combustion engine mounted in a vehicle or the like for the purpose of improvement in brake thermal efficiency, improvement in exhaust emission, reduction in specific fuel consumption, or the like.
An internal combustion engine provided with an intake and exhaust valve driven to open and close by electromagnetic force, i.e. what is known as an electromagnetic valve train, is known as an example of a variable valve train. In an internal combustion engine provided with this type of electromagnetic valve train, because there is no need to drive the intake and exhaust valve to open and close using the rotation force of the engine output shaft, mechanical loss originating in the drive of the intake and exhaust valve is prevented. Moreover, in the internal combustion engine provided with the electromagnetic valve train, it is possible to arbitrarily alter the valve opening time and the opening and closing timing of the intake and exhaust valve, so that pump loss of the internal combustion engine caused by a throttle valve can be suppressed.
However, in a non-throttle operation-controlled internal combustion engine, because almost no pump loss of the internal combustion engine is generated, there is no negative pressure in the combustion chamber of the internal combustion engine during deceleration of the vehicle. As a result, the problem arises that the engine braking effect is diminished.
In response to this, control methods for internal combustion engines, such as that described in JP Laid-Open No. HEI 10-331671, have been proposed. The control method for an internal combustion engine described in the above publication aims at increasing the engine braking effect in an internal combustion engine provided with electromagnetic intake and exhaust valves and non-throttle operation-controlled with these electromagnetic valves. In this control method, the electromagnetic valves are controlled to increase the pump loss of the internal combustion engine. Thus, negative pressure is generated within the cylinders of the internal combustion engine, thereby increasing the engine brake effect.
An object of the invention is to provide, in an internal combustion engine provided with a variable valve train capable of arbitrarily altering the opening and closing timing and/or the amount of opening of at least one of an intake valve and an exhaust valve and a negative pressure mechanism for operating using intake pipe negative pressure generated in an intake passage of the internal combustion engine, a technology capable of ensuring negative pressure according to the operation of the negative pressure mechanism.
The internal combustion engine having a variable valve train according to the first aspect of the invention includes: a variable valve train capable of adjusting opening and closing timings and/or opening amounts of at least one of an intake valve and an exhaust valve of an internal combustion engine; a negative pressure mechanism that operates using intake pipe negative pressure generated in an intake passage of the internal combustion engine; and negative pressure supply device that supplies negative pressure to the negative pressure mechanism when a predetermined condition is satisfied.
In the thus structured internal combustion engine, the negative pressure supply device supplies negative pressure to the negative pressure mechanism when a predetermined condition is satisfied. In this case, the desired negative pressure is supplied to the negative pressure mechanism with no need of altering the mode of operation of the variable valve train. Namely, the desired negative pressure is supplied to the negative pressure mechanism without there being any effect on the operating state of the internal combustion engine.
A vacuum pump can be taken as an example of the negative pressure supply device according to the invention.
The predetermined condition according to the invention can be exemplified as follows: the intake pipe negative pressure for operation of the negative pressure mechanism is insufficient; or a predetermined time period has passed since the negative pressure supply device finally supplied the negative pressure to the negative pressure mechanism. The above-mentioned predetermined time period may be a value determined using time as a parameter, or may be a value determined using a running distance of a vehicle provided with the internal combustion engine as a parameter.
Examples of the variable valve train according to the invention include: an electromagnetic valve train for driving the intake valve and/or the exhaust valve using the electromagnetic force; a hydraulic valve train for driving the intake valve and/or the exhaust valve using hydraulic pressure; and a mechanical variable valve train for, in an internal combustion engine provided with a camshaft that drives the intake valve and/or the exhaust valve to open and close using the rotation force of a crankshaft, altering the rotation phase of the camshaft relative to the crankshaft.
The internal combustion engine having a variable valve train according to the second aspect of the invention includes: a variable valve train capable of adjusting opening and closing timings and/or opening amounts of at least one of an intake valve and an exhaust valve of an internal combustion engine; a negative pressure mechanism that operates using intake pipe negative pressure generated in an intake passage of the internal combustion engine; a throttle valve for adjusting a flow rate of intake air flowing through the intake passage; and negative pressure generating device that generates intake pipe negative pressure by controlling the variable valve train and the throttle valve when a predetermined condition is satisfied.
In the thus structured internal combustion engine, when the predetermined condition is satisfied, the negative pressure generating device generates intake pipe negative pressure using the variable valve train and the throttle valve in combination. At this time, the negative pressure generating device may also, for example, control the variable valve train such that the internal combustion engine pump efficiency is increased, and close the throttle valve by a predetermined opening amount.
In this case, because intake pipe negative pressure is generated using the variable valve train and the throttle valve in combination, it is easier to control the operating state of the internal combustion engine compared to when intake pipe negative pressure is generated using solely the variable valve train, and it is also easy to control the torque of the internal combustion engine.
The predetermined condition according to the invention can be exemplified as follows: the intake pipe negative pressure for operation of the negative pressure mechanism is insufficient; a predetermined time period has passed since the negative pressure supply device finally supplied the negative pressure to the negative pressure mechanism; or a vehicle provided with the internal combustion engine is traveling in a deceleration state.
Examples of the variable valve train according to the invention include: an electromagnetic valve train for driving the intake valve and/or the exhaust valve using the electromagnetic force; and a mechanical variable valve train for, in an internal combustion engine provided with a camshaft that drives the intake valve and/or the exhaust valve to open and close using the rotation force of a crankshaft, altering the rotation phase of the camshaft relative to the crankshaft.
Moreover, when intake pipe negative pressure needs to be generated, it is also possible for the negative pressure generating device according to the invention to control the variable valve train and the throttle valve such that no variation is generated in the torque of the internal combustion engine.
Further, when intake pipe negative pressure needs to be generated, it is also possible for the negative pressure generating device according to the invention to control the variable valve train and the throttle valve such that the torque required by the internal combustion engine and the actual torque of the internal combustion engine match. At this time, it is preferable if the required torque is decided with the number of revolutions of the internal combustion engine and the accelerator opening angle as parameters.
An internal combustion engine having a variable valve train according to the third aspect of the invention includes: a variable valve train capable of adjusting an opening and closing timing and/or opening amount of at least one of an intake valve and an exhaust valve of the internal combustion engine; a negative pressure mechanism that operates using an intake pipe negative pressure generated in an intake passage of the internal combustion engine; a throttle valve for adjusting a flow rate of intake air flowing through the intake passage; and throttle valve controller that closes the throttle valve by a predetermined amount when a predetermined condition is satisfied.
In the thus structured internal combustion engine having the variable valve train, the throttle valve controller that closes the throttle valve by the predetermined amount when the predetermined condition is satisfied. In this case, the intake pipe negative pressure is generated in the intake passage downstream of the throttle valve. As a result, the intake pipe negative pressure for operation of the negative pressure mechanism is secured.
The predetermined condition according to the invention can be exemplified as follows: the intake pipe negative pressure for operation of the negative pressure mechanism is insufficient; a predetermined time period has passed since the negative pressure supply device finally supplied the negative pressure to the negative pressure mechanism; or a vehicle provided with the internal combustion engine is traveling in a deceleration state.
An internal combustion engine having a variable valve train according to the fourth aspect of the invention includes: a variable valve train capable of adjusting an opening and closing timing and/or opening amount of at least one of an intake valve and an exhaust valve of the internal combustion engine; a negative pressure mechanism that operates using an intake pipe negative pressure generated in an intake passage of the internal combustion engine; a throttle valve for adjusting a flow rate of intake air flowing through the intake passage; throttle valve controller that closes the throttle valve by a predetermined amount when a predetermined condition is satisfied; and valve train controller that, in a case where the throttle valve control means closes the throttle valve by the predetermined amount, controls the variable valve train so as to alter the opening and closing timing and/or opening amount of at least one of the intake valve and the exhaust valve with respect to a case where the throttle valve controller does not close the throttle valve by the predetermined amount.
At this time, the valve train controller may control the variable valve train such that required torque for the internal combustion engine matches actual torque thereof, or may control the variable valve train so as to suppress torque variation of the internal combustion engine. Note that the required torque may be determined by using a number of revolutions of the internal combustion engine and an accelerator opening amount as parameters.
An internal combustion engine having a variable valve train according to the fifth aspect of the invention includes: a variable valve train capable of adjusting an opening and closing timing and/or opening amount of at least one of an intake valve and an exhaust valve of the internal combustion engine; a negative pressure mechanism that operates using an intake pipe negative pressure generated in an intake passage of the internal combustion engine; a throttle valve for adjusting a flow rate of intake air flowing through the intake passage; intake air amount controller that controls the variable valve train to adjust an intake air amount of the internal combustion engine while retaining the throttle valve at a predetermined opening amount, when an operating state of the internal combustion engine is in a predetermined operating region; and throttle valve controller that closes the throttle valve by a predetermined amount from the predetermined opening amount when a predetermined condition is satisfied while the intake air amount controller is controlling the intake air amount of the internal combustion engine.
In the thus structured internal combustion engine having the variable valve train, so-called non-throttle operation control is conducted when the operating state of the internal combustion engine is in the predetermined operating region. More specifically, when the operating state of the internal combustion engine is in the predetermined operating region (e.g., in a low/medium load operating region), the intake air amount controller controls the variable valve train to adjust the intake air amount of the internal combustion engine while retaining the throttle valve at the predetermined opening amount (e.g., at a substantially fully open position).
If the predetermined condition is satisfied while the operating state of the internal combustion engine is in the predetermined operating region, in other words, while the intake air amount controller is conducting the non-throttle operation control, the throttle valve controller closes the throttle valve by the predetermined amount from the predetermined opening amount. In this case, the intake pipe negative pressure is generated in the intake passage downstream of the throttle valve, so that the negative pressure can operate using the intake pipe negative pressure.
An internal combustion engine having a variable valve train according to the sixth aspect of the invention includes: a variable valve train capable of adjusting an opening and closing timing and/or opening amount of at least one of an intake valve and an exhaust valve of an internal combustion engine; a negative pressure mechanism that operates using an intake pipe negative pressure generated in an intake passage of the internal combustion engine; a throttle valve for adjusting a flow rate of intake air flowing through the intake passage; intake air amount controller that controls the variable valve train to adjust an intake air amount of the internal combustion engine while retaining the throttle valve at a predetermined opening amount, when an operating state of the internal combustion engine is in a predetermined operating region; an evaporation fuel reflux mechanism for refluxing evaporation fuel generated in a fuel tank of the internal combustion engine into the intake passage; and throttle valve controller that closes the throttle valve by a predetermined amount from the predetermined opening amount when the evaporation fuel reflux mechanism needs to be operated while the intake air amount controller is controlling the intake air amount of the internal combustion engine.
The thus structured internal combustion engine having the variable valve train may further include valve train controller that controls the variable valve train such that the intake air amount of the internal combustion engine does not change, when the throttle valve controller closes the throttle valve by the predetermined amount in order to operate the evaporation fuel reflux mechanism. In this case, the intake pipe negative pressure for operation of the evaporation fuel reflux mechanism can be secured without changing the intake air amount of the internal combustion engine.
Examples of the variable valve train according to the invention include: an electromagnetic valve train for driving the intake valve and/or the exhaust valve to open and close using the electromagnetic force; a hydraulic valve train for driving the intake valve and/or the exhaust valve to open and close using hydraulic pressure; a mechanical variable valve train for altering the rotation phase of a camshaft that drives the intake valve and/or the exhaust valve to open and close using the rotation force of a crankshaft; and an appropriate combination of the above-mentioned valve trains.